Before employing any doctor to work in your surgery you must check:

• That the doctor to be employed in the Wessex region is on an English PCT's Performers List.
• That the doctor has the necessary medical defence cover. 
• 2 clinical references;
  - These must relate to a recent post that was held for at least 3 months without a significant break.
  - If this is not possible a full explanation and alternative references must be followed up.
• If a locum is required to work immediately the doctor may be engaged for a single period of up to 14 days while references are followed up and for an additional 7 days if the referee is ill, on holiday or otherwise temporarily unavailable.
• If the doctor is employed on more than one occasion in a three month period the employing doctor may rely on the references provided on the first occasion, provided they are not more than 12 months old. 
• You should always check that a doctor is registered with the GMC as part of your pre-employment checks.
• Since April 2006 doctors appointed as  GPs must, in addition since April 2006 be on the GP Register
  

This link takes you to a more detailed email sent to

all practices on 20 Feb 2007 about the pre-employment checks

that must be undertaken on all doctors, locums and partners.

Pre-employment checks on doctors

And further guidance from the GMC is here

GMC guidance on employing a doctor